Electrical cross-over

The protons produced at the anode cross over the membrane, ensuring the electrical conductivity inside the electrolyte, whereas the electrons liberated at... 

L-dopa, a precursor of the neurotransmitters norepinephrine and dopamine, was introduced into HE therapy by J.D. Parkes et al. in 1970. The results were good. As yet, there is still no accepted opinion on the use of this substance. Piracetam, as a nootropic substance, led to a clear improvement in typical electrical brain activities in animals displaying hepatic damage and symptoms of encephalopathy. Similarly, a double-blind randomized cross-over study with the nootropic agent centropheno-xine partly showed positive effects in psychometric testing. Bromocriptine, an agonist of the dopamine receptor, was also used in 1980 for chronic hepatic encephalopathy. (146,163) Application of L-carnitine (6 g/day orally, divided into two doses, for 4 weeks) leads to a marked reduction of hyperammonaemia and a clear improvement in clinical symptoms of HE in cirrhotic patients. (119) (s. p.49)... 

A field emission source uses a needle-like tungsten or carbon tip as the cathode, shown in Fig. 14.28. The tip is only nanometers wide, resulting in a very high electric field at the tip. Electrons can tunnel out of the tip with no input of thermal energy, resulting in an extremely narrow beam of electrons. Electron beams from heated filaments have a focal (cross-over) diameter of about 50 p,m while a field emission source has a crossover diameter of only about 10 nm. Field emission sources can serve as probes of surfaces at the nanometer scale (an Auger nanoprobe). 

Halkier-Sorensen and Thestrup-Pedersen [40] utilized a cross-over study to evaluate the efficacy of a moisturizer (Locobase, Yamanouchi Europe B. V. Research Laboratories, Leiderdrop, The Netherlands) among cleaners and kitchen assistants during daily work. The population was divided into two groups 56 workers used the test moisturizer only on their hands for the first 2 weeks and no emollient during the subsequent 2 weeks, and vice versa (n = 55). The moisturizer prevented the development of skin dryness. Electrical capacitance (epidermal hydration) decreased significantly when the study subjects were not using the moisturizer but, unexpectedly, there was no increase in the TEWL rates or in skin temperature. 

Semiconductors comprise that class of solids whose electrical properties are intermediate between insulators and good metallic conductors. In a semiconductor the energy gap between the filled valence band and the next conduction band is rather low. For example, in diamond it is 589 kJ/mol whereas for silicon (a semiconductor) it is 105 kJ/mol and in germanium it is 69 kJ/mol. At low temperatures the energy is not sufficient to cross the forbidden zone and the material remains a poor conductor or insulator. As the temperature is increased a few electrons acquire sufficient energy to cross over the forbidden zone and occupy the empty conduction bands. Thus the substance is able to conduct current. 

In addition, the nse of this term enables us to take acconnt of the fact that the measnred no-load voltage of an electrochemical cell is not eqnal to the difference in thermodynamic potentials of the electrodes. Certain anthors give it a physical interpretation expressing two parasitic phenomena a leakage of electric current into the electrolyte, and the permeation of the reagents across the electrolyte (termed cross-over ) [LAR 00],... 

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